Jet propulsion system

Abstract

A jet propulsion system for a small watercraft including an arrangement for isolating the sound of water flowing through the water inlet portion of the jet propulsion unit from the occupants of the watercraft. This silencing is provided by providing a double wall on at least the portion of the jet propulsion unit water inlet portion juxtaposed to the passenger compartment to provide an insulating jacket. Water may be filled in the insulating jacket and this water can be derived by filling it with the coolant which is circulated through the engine.

I claim: 
     
       1. A watercraft comprised of a hull, a jet propulsion unit mounted by said hull for propulsion of said watercraft, said jet propulsion unit being comprised of an outer housing comprised of a water inlet portion forming a water inlet opening and water inlet duct for drawing water from the body of water in which said watercraft is operating, said water inlet portion of said outer housing terminating at an outer housing impeller portion containing an impeller for pumping the water and an outer housing discharge nozzle, and means for providing with said outer housing an enclosed sound insulation jacket extending around at least a portion of said jet propulsion unit outer housing from substantially said water inlet opening to substantially said impeller portion. 
     
     
       2. A watercraft as set forth in claim 1 wherein the sound insulation jacket is provided at least around a part of said outer housing surrounding an impeller shaft driving the impeller and extending through a part of the water inlet duct for connection to a driving engine. 
     
     
       3. A watercraft as set forth in claim 2 wherein the sound insulation is provided by a double wall section of the water inlet portion. 
     
     
       4. A watercraft as set forth in claim 3 further including means for filling the sound insulation jacket with water. 
     
     
       5. A watercraft as set forth in claim 4 wherein the means for filling the sound insulation jacket with water comprises means for circulating water through said sound insulating jacket. 
     
     
       6. A watercraft as set forth in claim 1 wherein the jet propulsion unit is mounted within a tunnel formed in the hull of the watercraft and which tunnel is juxtaposed to a passenger compartment. 
     
     
       7. A watercraft as set forth in claim 6 wherein the water inlet portion is mounted in the tunnel in an area in proximity to a seat within the rider's area. 
     
     
       8. A watercraft as set forth in claim 1 wherein the sound insulation jacket is provided at least around a part of said outer housing surrounding a part of the water inlet duct for connection to a driving engine. 
     
     
       9. A watercraft as set forth in claim 8 wherein the sound insulation is provided by a double wall section of the water inlet portion. 
     
     
       10. A watercraft as set forth in claim 9 further including means for filling the sound insulation jacket with water. 
     
     
       11. A watercraft as set forth in claim 10 wherein the means for filling the sound insulation jacket with water comprises means for circulating water through said sound insulating jacket.